What is aircrack?
Aircrack is a set of tools for auditing wireless networks:
 * airodump: 802.11 packet capture program
 * aireplay: 802.11 packet injection program
 * aircrack: static WEP and WPA-PSK key cracker
 * airdecap: decrypts WEP/WPA capture files
The official download location is http://www.cr0.net:8040/code/network/.
However, if you can't access port 8040 for some reason, you may use this mirror instead: http://100h.org/wlan/aircrack/.
Additional Information:
The information has been provided by Christophe Devine.
To keep updated with the tool visit the project's homepage at: http://www.cr0.net:8040/code/network/